BMI Calculators
Body Mass Index calculators for adults, children, athletes, and special populations
Calculators & Tools
BMI Calculator for Kids
BMI Calculator for Kids converts height and weight into a BMI-for-age percentile using CDC growth chart LMS parameters (ages 2–19). Enter child's sex, age in years and months, height, and weight to get BMI, percentile position, CDC weight category (Underweight/Healthy/Overweight/Obese/Severe Obesity), healthy weight range for the age, and the exact BMI thresholds at the 5th, 85th, and 95th percentiles for that age and sex. Includes a visual percentile bar and BMI threshold table.
BMI Body Fat Calculator
The BMI Body Fat Calculator estimates body fat percentage from BMI, age, and sex using the Deurenberg formula (BF% = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4). It outputs BMI with WHO category, estimated body fat with ACE category, and a Normal Weight Obesity (NWO) alert when BMI is normal but body fat is in the Acceptable or Obese ACE range. Supports metric and imperial. Accuracy is approximately ±4.1 percentage points; use DEXA or hydrostatic weighing for clinical precision.
BMI Calculator
The BMI Calculator computes your Body Mass Index using your height and weight, then maps the result against WHO classification categories from underweight through to obese Class III. It supports both metric (kg and cm) and imperial (lbs and feet/inches) inputs. Use it to establish a baseline, set a healthy weight target, or monitor progress over time.
BMI Weight Loss Calculator
The BMI Weight Loss Calculator works out the exact weight you need to reach to achieve a healthy BMI, given your height and current weight. It shows three simultaneous targets: upper healthy (BMI 24.9), mid healthy (BMI 21.7), and lower healthy (BMI 18.5), along with the kilograms to lose for each and time estimates at 0.5 and 1 kg per week. Supports metric and imperial. Use it to turn a BMI category label into a specific, actionable weight target.
BMI Calculator for Older Adults
BMI Calculator for Older Adults (65+) applies ESPEN and WHO senior-adjusted BMI thresholds: healthy range is 22–26.9 (not 18.5–24.9), underweight is below 22, and BMI 27–29.9 is flagged as potentially protective due to the obesity paradox. Includes optional waist circumference input with AHA risk thresholds, sarcopenia and malnutrition risk alerts at BMI below 22, obesity paradox context panel at BMI 27–29.9, standard WHO categories shown alongside senior-adjusted categories, and healthy weight range for the entered height using the 65+ BMI targets. Supports metric and imperial.
BMI Calculator for Women
The BMI Calculator for Women computes Body Mass Index and adds two female-specific outputs: an estimated body fat percentage using the Deurenberg formula for women (BF% = 1.20 × BMI + 0.23 × Age − 5.4) and a waist circumference risk assessment against the AHA threshold of 88 cm (35 inches) for women. Enter height, weight, age, and optional waist measurement to get a complete female body composition picture alongside the WHO BMI category.
BMI Prime Calculator
The BMI Prime Calculator computes BMI from height and weight and expresses it as a ratio against the upper limit of the healthy BMI range: BMI Prime = BMI divided by 25 (standard WHO) or 23 (Asian WHO WPRO). A BMI Prime of 1.00 means your BMI exactly equals the healthy ceiling. Values above 1.00 show the percentage excess above normal, with BMI Prime 1.20 meaning 20% above the healthy upper limit. The calculator also shows the exact weight to gain or lose to reach BMI Prime 1.00 at your height, and the full healthy weight range. Supports metric, imperial, and Asian population reference.
BMI Percentile Calculator
The BMI Percentile Calculator computes BMI from height and weight and then shows where that BMI falls in the US adult population distribution as a percentile rank, using sex-specific NHANES 2015-2018 reference data for adults aged 20 and over. A result of 65 means the BMI is higher than 65% of US adults of the same sex. The tool also shows WHO category, a visual distribution bar, and key context: the US median adult BMI is approximately 27.7 for both sexes, placing it in the WHO overweight category.
BMI Calculator for Athletes
BMI Calculator for Athletes calculates standard BMI alongside FFMI (Fat-Free Mass Index) and body fat category for athletes and muscular individuals. Enter height, weight, sex, and optional body fat percentage (from DEXA, calipers, or BIA) for BMI with WHO category, ACE body fat category, normalized FFMI with natural muscular limit context, lean mass and fat mass breakdown, an athletic misclassification alert when BMI is elevated but body fat is in the athlete range, and a sport-specific BMI reference table for 12 disciplines. Supports metric and imperial.
BMI Calculator for Men
The BMI Calculator for Men computes your Body Mass Index and adds two male-specific outputs: an estimated body fat percentage using the Deurenberg formula and a waist circumference risk assessment against the AHA threshold of 102 cm (40 inches) for men. Enter your height, weight, age, and optional waist measurement to get a complete male body composition picture alongside the standard WHO BMI category.
BMI Calculator for Teenagers
BMI Calculator for Teenagers converts height and weight into a CDC BMI-for-age percentile for teenagers aged 13 to 19. Enter sex, age in years and months, height, and weight for instant BMI, percentile, CDC category (Underweight/Healthy Weight/Overweight/Obese/Severe Obesity), healthy weight range, and the BMI thresholds at the 5th, 85th, 95th, and 120%-of-95th percentiles for that exact age and sex. Includes puberty context, athletic misclassification warning, eating disorder awareness banner with helpline links, and a visual percentile bar.
BMI Calculator for Pregnancy
The BMI Calculator for Pregnancy works out pre-pregnancy BMI from height and pre-pregnancy weight and maps it to the IOM 2009 gestational weight gain guidelines for singleton and twin pregnancies. It outputs the recommended total weight gain range for your BMI category, the second and third trimester weekly gain rate, and an optional week-by-week tracking panel comparing current gain against the IOM expected range. Supports metric and imperial.
Ponderal Index Calculator
The Ponderal Index Calculator computes the Ponderal Index (PI), also called Rohrer's Index or the Corpulence Index, from height and weight using the formula PI = weight(kg) / height(m)³. Unlike BMI, which divides by height squared, PI divides by height cubed and is significantly more stable across different statures. It supports metric and imperial inputs and shows your BMI alongside your PI for direct comparison, including the normal weight range for your height under both metrics.